1. Field of the Invention
The present invention relates to a system for hermetically sealing a thermoplastic tube containing a liquid, which system has two modes of operation; one in which the tube sealing portion of the system is hand-held and the second in which the tube sealing portion is mounted in a fixed position.
2. Description of the Prior Art
The need to collect blood from donors is ongoing and occurs wherever modern medicine is practiced, particularly in the larger urban centers. As a result, blood collection centers have been established at fixed, or permanent, locations. In addition, mobile blood collection units are employed to serve remote areas or to obtain blood from donors at locations where large numbers of potential donors are to be found such as shopping centers, factories, office buildings and the like.
The process of collecting blood from the donor is relatively straightforward from the donor's perspective, but the means for storing, preserving, and classifying the blood collected requires sophisticated techniques and equipment to minimize the loss of blood and to minimize the risk of contaminating collected blood while still making it possible to obtain samples of collected blood, plasma and the like materials derived from human blood under the most hygienic conditions.
Typically a predetermined amount of blood is collected from a donor within a collector bag by means of tubing connected to a needle through which blood from a donor is drawn. It is preferable to be able to seal the collection tube in close proximity to the needle in order to maintain sterility of the collected blood, or at least to prevent contamination from sources outside of the donor prior to withdrawal of the needle from the donor's arm. Under such circumstances the maximum usable amount of blood is obtained with the highest probability of maintaining it free from external contaminating influences. To facilitate classifying and testing blood once collected as well as the separated components of blood when processed, the collection tube, or equivalent, may be sealed to provide several compartments, or segments, with each containing sufficient amounts of the fluid so that tests can be made for example to classify the contents of the fluid in a collection bag while maintaining the fluid in the bag sterile, by not subjecting it to external sources of contamination.
There is a need for a tube sealer system to hermetically seal tubes which are made of a thermoplastic material such as polyvinylchloride (PVC) at the collector sites where donors give blood as well as at the processing centers where blood is typed and processed into various components, for example. At collector sites a hand-held sealer is needed to bring the sealer to the tube to be sealed while the tube is still connected to the needle in the donor's arm. At processing centers, it is frequently more convenient to bring the tubing to be sealed to a sealer which is in a fixed position.
Prior art tube sealing systems have provided either for a hand-held sealer, or a fixed substantially immoveable sealer. As a result, no one sealer system is capable of performing all of the tube sealing functions associated with the collection, processing, and using of blood and blood derivatives as required by modern health service systems.
Prior art tube sealing systems have also had a problem with "burn through" which occurs when the thermoplastic material of the tubing is either overheated by the dielectric heating process using an RF field between a pair of electrodes, or the electrodes squeeze the walls of the tube so that too little material of the walls of the tubing remain, with the result that the tube on either side of the electrodes is not properly sealed. As a result, the liquids in the tubes can escape and the contents are subject to external contamination, and thus are no longer sterile.
Prior art tube sealing systems have attempted to prevent burn through by controlling the amount of RF power used to heat the dielectric material from which the tubes are made. Such tube sealing systems have done so by controlling the amount of RF power applied to heat the tubing and the time that the RF power is applied to the electrodes between which the tubing is located. Such systems are not particularly satisfactory in controlling the amount of heating of the material of the tubing and thus increase the risk of burn through because of the many other variables that affect the amount of heat induced in the dielectric material which includes the material itself, the liquids in the tubing, etc. Thus better means for controlling the sealing process are needed other than by attempting to control or vary the magnitude of the RF power supplied, or the time that the RF power is supplied, or both.